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5/4/12

Meat originating from U.S. horses may
contain residues from substances banned by the U.S. Food and Drug
Administration and the European Union for use in animals intended for
consumption. Phenylbutazone, for example, is commonly administered to
U.S. horses and has been associated with life- threatening reactions
in humans. Requiring a thorough drug history for each U.S. horse
intended for human consumption may help circumvent human health
risks.

In t r o d u c t i o n

According to the Food and Agriculture
Organization of United States, an estimated 9.5 million horses reside
in the United States.1 The American Veterinary Medical Association
defines the horse as a "companion animal," along with dogs
and cats.2 Horses are utilized for service, recreation, and
competition in the United States.3 Despite their multi-faceted views
of the horse, the U.S. population largely considers the consumption
of horse meat taboo.4 In the state of California, for instance,
eating horse meat is restricted under the state's Criminal Code5 and
horse slaughter is illegal in Florida6 and Illinois.7 Given the
attitude towards equids and the lack of demand for horse meat in the
United States, they are defined as non-food producing animals by the
Food and Drug Administration (FDA).8

Despite the U.S. population's
disinterest in horse meat, it remains a part of the diet of some
consumers in other countries, such as France, Japan, and Italy.9 In
2007, a combination of state laws prohibiting horse slaughter and a
simultaneous de-funding of United States Department of Agriculture
(USDA) inspections by Congress10 lead to the closure of the few,
mainly foreign-owned, horse slaughter plants that operated within the
United States.11,12,13 In November 2011, this defunding of USDA horse
slaughter inspections was omitted from a spending bill signed into
law. While new funds are not being provided for the USDA's resumption
of horse meat inspections, the ban on domestic horse slaughter has
been lifted.14

The 2007 provisions did not end the
slaughter of U.S. horses for human consumption. Rather, the closing
of U.S. slaughterhouses almost doubled the production of horse meat
in Canada in 2007, with approximately 40% of the horses being
slaughtered imported from the U.S.15 In 2012, the European

Commission released their findings of a
2011 audit which noted that 85% of the horses slaughtered in a
Canadian processing plant originated from the United States.16 The
United States also exports its horses to plants in Mexico for local
and foreign consumption.17

Since U.S. horses are primarily used
for companionship and competition rather than consumption, drugs may
be administered without taking food safety implications into account.
This is especially pertinent in regards to the administration of the
substance phenylbutazone (PBZ). The presence of PBZ - as well as many
other FDA-banned substances - in U.S. horses destined for slaughter
results in the high likelihood of contaminated horse meat, which poses
a potentially serious risk to the health of human consumers.18,19

Phenylbutazone

In 1949 the potent non steroidal
anti-inflammatory drug (NSAID) PBZ became available as a treatment in
the United States for people suffering from both rheumatoid arthritis
and gout. However, within three years of its availability, PBZ was
linked to serious adverse reactions, including aplastic anemia, bone
marrow depression, renal failure, and even death. After examining
several case studies of PBZ use, the FDA banned PBZ for human use in the
United States.20 According to the FDA:

“Phenylbutazone is known for its
ulcerogenic, nephrotoxic, and hemotoxic effects in horses, dogs,
rats, and humans. It is known to induce blood dyscrasias, including
aplastic anemia, leucopenia, agranulocytosis, thrombocytopenia, and
deaths. The reported adverse reactions were associated with the human
clinical use of 200 to 800 milligrams phenylbutazone per day€¦.[I]t
is unclear what level of exposure would be required to trigger such
reactions in sensitive people. Moreover, phenylbutazone is a
carcinogen, as determined by the National Toxicology Program (NTP)
based on positive results in genotoxicity tests and some evidence of
carcinogenicity seen in the rat and mouse in carcinogenicity
bioassays NTP conducted.”21

For animals, the only FDA-approved
phenylbutazone use is as an oral or injectable dose in dogs and
horses.22,23 As it stands, PBZ use in humans and food-producing
animals alike remains unapproved.24

Phenylbutazone in Thoroughbreds Bound
for Slaughter: A Case Study

There can only be one winner at the end
of each horse race, and many of the horses that do not place, show
signs of injury, or are past their prime are sent to auction, and
ultimately end up in slaughterhouses in Canada or Mexico.25 The
European Union (EU) has found that horse meat originating from
Mexican slaughterhouses contain harmful residues of several EU
prohibited substances such as clenbuterol (bronchodilator),
zilpaterol (used as a steroid substitute), and furanics (anabolic
steroid).26,27 Due largely to over-breeding, the thoroughbred racing
industry is one of the principal contributors to the estimated
133,241 U.S. horses slaughtered in 2011.28,29

Because of the intense training and
racing endured by these horses, many develop musculoskeletal

injuries that trainers and owners treat
with NSAIDs, of which PBZ is the common due to its legality in the
racing industry. A study done by the Daily Racing Form found 99% of
racehorses in California and 92% of horses at Suffolk Downs in
Massachusetts are given PBZ on a regular basis.30 Certain racetracks
allow only PBZ administration on race day, but all usage must be
recorded on the horse's track record.31 This documentation
requirement makes racing thoroughbreds convenient candidates for a
case study of PBZ usage in U.S. horses bought for slaughter.

Nicholas Dodman of Tufts University
Cummings School of Veterinary Medicine, Nicolas Blondeau of the
Institut de Pharmacologie Moléculaire et Cellulaire, and Ann Marini
of Uniformed Services

University of the Health Sciences
conducted a study to investigate whether thoroughbred race horses
were given PBZ prior to being bought for human consumption, and to
see how widely the FDA ban on PBZ usage in horses that end up on
consumers' plates is ignored. The study identified 50 thoroughbreds rescued from slaughter and 18
thoroughbreds that were sent to slaughter. Each horse's Jockey Club
lip tattoo allowed the researchers to find the registered name of all
68 horses, and each horse's drug record was obtained from their race
track records.32

Upon review of the records, one of the
horses sent to slaughter was not documented as receiving PBZ but the
drug was identified in his blood test results, and another
thoroughbred was administered PBZ by a veterinarian in the same month
he was sent to slaughter. The remaining 16 of the 18 horses
slaughtered and all 16 of the rescued horses were recorded as
receiving PBZ within 24 hours of a race. Data collected by the
researchers determined that the time interval between horse's last
known dose of PBZ and the date they were bought for slaughter varied
from a week to four years. However, it is important to note that the
FDA, the EU, the United Kingdom, and Canada do not allow any use of
PBZ in horses intended for human consumption regardless of withdrawal
time.33

Another important aspect in
understanding the risk of PBZ contamination in horse meat is the
circulation of PBZ in the bloodstream. Horses possess 1.76 times the
amount of blood per pound of body weight compared to cattle. With
this much blood, it is possible that high-volume slaughterhouses€”one
Canadian slaughterhouse processed 100 horses a days€”do not allow
sufficient time for the horse's blood to be completely drained from
the muscle, increasing the risk of meat contamination.34

The findings of Dodman, et al.,
indicate a serious discontinuity between food safety regulations and
practice. Horses with a history of PBZ use are making their way to
slaughter plants despite the United States' and other countries' ban
of the use of the drug in food producing animals.

The European Union's Evaluation of
Imported Horse Meat

In 2010, The European Commission's Food
and Veterinary Office (FVO) evaluated food safety standards of
imported equine meat from third countries (non-members of the
European Union).35 The FVO have found that many third countries -
such as Mexico, Canada, and the United States - do not keep
veterinary pharmaceutical treatment records for horses; and there are
no systems in place to differentiate equines intended for human consumption from all
other equines. The evaluations also reported that third countries
tolerate the administration of substances that are prohibited or
unauthorized in food-producing animals in the EU.36,37 The United
States has no official controls in place to verify the authenticity
or reliability of the medical records and equine documents now
required for horses destined for slaughter, only records of physical
identification are required.38 These discoveries prompted the
European Commission to facilitate corrective measures to their own
regulations regarding imported horse meat, and to require third
countries to implement action plans addressing compliance with the
EU's requirements regarding equine meat.39

Since 2000, the EU's regulations state
that horse meat cannot contain residues of veterinary medicinal
products exceeding previously set limits or residue from substances
banned for use in food producing animals in the EU. These
restrictions include phenylbutazone. If substances prohibited for use
in food- producing animals are administered to equids, those animals
must be excluded from the food chain.40 Finally, imported horse meat can only
be authorized if equines are included in European Commission-
approved residue control plans in third country slaughterhouses.41

Both Canada and Mexico have submitted
action plans in order to comply with the EU's import requirements for
equine meat, and both plans have been approved by the FVO.42

In Mexico, horses imported for
slaughter are to be microchipped and border controls have been
strengthened. A sworn statement on veterinary medical treatments is
requested for all slaughter horses, no matter what their country of
origin. United States providers of imported horses (holding
facilities) have been targeted in samplings of the Mexican National
Residue Monitoring Programme (NRMP). According to the NRMP nineteen
samples of horse meat in 2008, nine in 2009, and six in 2010 tested
positive for residues of banned substances. All of the horses who
tested positive were covered by a declaration stating that no
treatments were given to the horses, and all of these horses came
from U.S. providers. 43

In Canada, the Canadian Food Inspection
Agency (CFIA) has implemented the Equine Information Document (EID).
The EID contains a physical description of the animal, record of the
animal's medical treatment for the previous six months, and requires
the signature of the animal's owner at the time of ownership transfer
to verify that all information is accurate. Horses bought for
intended slaughter must have their EIDs also signed by the transient
agent responsible for the care of the equine from time of purchase
for slaughter until arrival at the meat processing establishment.
Each CFIA inspected facility engaged in equine slaughter must
present an EID for all domestic and imported equines presented for
slaughter. If the EID indicates a horse has been given a substance
not permitted for use in equine slaughtered for food, such as
phenylbutazone, the horse will not be eligible for slaughter.44
However, the 2011 FVO audit noted "for those horses imported
from the United States of America for direct slaughter, the equine
identification documents received were not reliable..." The
audit further noted that 85% of the horses slaughtered in this
Canadian processing plant originated from the U.S. and all of these
horses were imported for direct slaughter.45 Considering cases such
as the one above, as long as there is no identification system in
place, U.S. horses will not meet the European Commission's new food
safety regulations, which will become effective in July 2013.

The European Commission mandated a
transitional period of three years in which third countries have to
provide guarantees regarding medical and drug history for horses
during their last six months before slaughter. After the three-year
transition period - which ends in 2013 - guarantees must be provided
for the lifetime of the horses.46 This policy would complement the
EU's "horse passport" legislation, which requires records
to be kept of certain medicinal products.47 This required lifetime
guarantee that a horse be cleared of all EU prohibited substances for
use in food-producing animals could eliminate virtually all U.S.
horses from the food chain. The substances banned for use in
food-producing animals routinely administered by U.S. horse owners
render most American horses ineligible for foreign slaughter. 48

Conclusion

The slaughter of U.S. horses poses a
potentially serious health risk to human consumers, yet thousands are
still slaughtered and sold to consumers. New measures put in place in
the European Union to address the human health risk associated with
horse slaughter are vital steps to insure U.S. horses, who are
regularly given phenylbutazone along with other EU-banned substances,
are kept out of the slaughter pipeline.

Prevention needs to start within U.S.
borders. The United States should look to the European Union's horse
passport and Canada's Equine Identification Document (EID)
benchmarks. Requiring accurate medical records and identification
documents, regardless of the horse's intended use, would draw clear
lines regarding each individual horse's eligibility for human
consumption. Until such a system is in place, meat from American
horses may pose a public health threat.

Horses: For oral use in horses for the
relief of inflammatory conditions associated with the musculoskeletal
system.
www.fda.gov/downloads/AnimalVeterinary/Products/ApprovedAnimalDrugProducts/FOIADrugSummaries/ucm061800.pdf.
Accessed April 12, 2012.

16 European Commission, 2011. Health
and Consumers Directorate-General. Final Report of an Audit Carried Out in Canada from 13 to 23
September 2011 in Order to Evaluate the Monitoring of Residues and
Contaminants in Live Animals and Animal Products, Including Controls
on Veterinary Medicinal Products.
ec.europa.eu/food/fvo/act_getPDF.cfm?PDF_ID=9456. Accessed April 12,
2012.

25 Rhoden, W.C. 2011. Racing Should
Care for Its Own. The New York Times, May 20, p. D5.
www.nytimes.com/2011/05/21/sports/racing-industry-should-care-for-its-own.html?_r=1.
Accessed April 12, 2012.

26 European Commission Health &
Consumers Directorate-General. 2011. Final Report of a Mission Carried Out in Mexico From 22 November
to 03 December 2010 in Order to Evaluate the Operation of Controls
Over the Production of Fresh Horse Meat and Meat Products Intended
for Export to the European Union as Well as Certification Procedures.
ec.europa.eu/foodfvorep_details_en.cfm?rep_id=2639. Accessed April
12, 2012.

27 European Commission Health and
Consumers Directorate-General. 2011. Imports of animals and their products from third countries. Sec
5.3.1.1.
ec.europa.eu/food/food/chemicalsafety/residues/third_countries_en.htm#5.3.1.1.
Accessed April 10, 2012.

28 Rhoden, W.C. 2011. Racing Should
Care for Its Own. The New York Times, May 20, p. D5.
www.nytimes.com/2011/05/21/sports/racing-industry-should-care-for-its-own.html?_r=1.
Accessed April 12, 2012.

37 European Commission Health &
Consumers Directorate-General. 2008. Final Report of a Mission
Carried Out in Mexico from 04 September to 11 September 2008 In Order
to Evaluate Public Health Control Systems and Certification
Procedures Over Production of Horse Meat Intended for Export to the EU. DG(SANCO)/2008-7979.

38 United States Department of
Agriculture. 2011. Animal Disease Traceability: A Guide to
Identifying Horses and other Equines for Interstate
Movement.
www.aphis.usda.gov/traceability/downloads/2011/FStrachorse.VS.pdf.
Accessed April 10, 2012.

39 European Commission Health and
Consumers Directorate-General. 2011. Imports of animals and their products from third countries. Sec
5.3.1.1.
ec.europa.eu/food/food/chemicalsafety/residues/third_countries_en.htm#5.3.1.1.
Accessed April 10, 2012.

40 European Commission Health and
Consumers Directorate-General. 2011. Imports of animals and their
products from third countries. Sec 5.3.1.1.

43 European Commission. 2010. Final
Report of a Mission Carried Out in Mexico From 22 November to 03 December 2010 In Order to Evaluate
the Operation of Controls Over the Production of Fresh Horse Meat and
Meat Products Intended for Export to the European Union as Well as
Certification Procedures. December 2010.
ec.europa.eu/food/fvo/rep_details_en.cfm?rep_id=2639. Accessed April
12, 2012.

45 European Commission, 2011. Health
and Consumers Directorate-General. Final Report of an Audit Carried Out in Canada from 13 to 23
September 2011 in Order to Evaluate the Monitoring of Residues and
Contaminants in Live Animals and Animal Products, Including Controls
on Veterinary Medicinal Products.
www.ec.europa.eu/food/fvo/index_en.cfm?reptoshow=2. Accessed April
12, 2012.

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